Depends on how much you trust your fellow man... For the most part, in camp grounds, you can leave most things out and they will be fine..
I've been burned a few times too, so I wouldn't leave much out and available that could be easily taken..
In my camping life, i've lost a sewer hose, ice chests, chairs, water skies, and just general vandalism in my 45+ years of camping life.. This includes camping since i was a kid with Mom and Dad in the early 70's.
I wouldn't leave my fridge on, with stuff in it.. One time, back when I was a kid and we had a seasonal site, we left the sewer hose and fridge going..
Someone took the hose and decided it would be fun to turn off the electric to the trailer... Came the next weekend to a warm fridge.. Just condiments for the most part, but taught us a big lesson in leaving stuff at the site.. It was a very nice place too...
Anyway, good luck with whatever you do and hope you have better luck with fellow man than I have had..
😞Mitch
2013 F150 XLT 4x4 SuperCab Max Tow Egoboost 3.73 gears #7700 GVWR #1920 payload. 2019 Rockwood Mini Lite 2511S.